Mesoscale and Nanoscale Physics
Hanbury Brown-Twiss interferometry at the $\nu=2/5$ fractional quantum Hall edge
Ryotaro Sano, Fumihiro Murabayashi, Daigo Ichikawa et al. (+5 more)
We propose a Hanbury Brown-Twiss interferometer for a $\nu=2/5$ fractional
quantum Hall edge system, in which quasiparticles tunnel between two co-propagating edge modes. In contrast to the previously studied anyonic Fabry-Pérot and Mach-Zehnder interferometers, the proposed setup relies purely on two-particle interference rather than single-particle interference. In the weak-tunneling regime, we employ a bosonized edge theory together with Keldysh perturbation theory to evaluate the cross-correlation of the tunneling currents. In the large-device limit, we obtain an analytic expression for the flux-dependent noise, whose structure closely resembles that of an electronic HBT interferometer, but with the electron charge replaced by the fractional charge $e^{\star}=e/3$ and with scaling dimensions characteristic of the fractional edge modes. In this limit, the explicit anyonic exchange phases cancel, whereas when the device size becomes comparable to the thermal length, the cross-correlation may recover a more explicit dependence on the anyonic statistical angle.
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All authors Ryotaro Sano, Fumihiro Murabayashi, Daigo Ichikawa, Thibaut Jonckheere, Jérôme Rech, Thierry Martin, Masayuki Hashisaka, Takeo Kato
Materials Science
Fully Atomic-Layer-Deposited Vertical Complementary FeRAM with Ultra-High 2Pr > 100 uC/cm2 and High Endurance > 1E10 cycles
Renhao Xue, Ruizhan Yan, Mansun Chan et al. (+1 more)
A limited remanent polarization (Pr) in HfO2-based FeRAM remains a key obstacle to density scaling and reliability, while material and process optimizations offer only incremental improvements. This limitation fundamentally originates from the thickness-constrained switchable polarization and the intrinsic polarization ceiling of HfO2-based ferroelectrics. Here, we propose an all-ALD-grown vertical complementary FeRAM (VCF) architecture, in which the top and bottom stacked FeRAM
cells maintain complementary polarization. This complementary dipole configuration converts the readout from a single-layer polarization response into a differential polarization summation, thereby amplifying the effective charge window without increasing the switching field of each individual layer or incurring area overhead. Viewed from top to bottom, an "up-down" polarization pair stores logic '1', whereas a "down-up" pair stores logic '0'. Using a complementary polarization write-read scheme, the VCF achieves an effective differential polarization above 100 uC/cm^2 and retains above 90 uC/cm^2 after 1e10 switching cycles without electrical breakdown. Robust retention (longer than 1e4 s at 85 degC) and strong disturb immunity are demonstrated, with an effective differential polarization above 80 uC/cm^2 under a V/3 scheme after 1e6 disturb pulses. Array-level operation is validated in a 5 x 5 selector-free crosspoint array. The performance enhancement of the VCF arises from the co-optimization of the all-ALD-grown process, device architecture, and operation scheme, enabling high density, a wide
memory window, and strong reliability for scalable FeRAM integration.
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All authors Renhao Xue, Ruizhan Yan, Mansun Chan, Xiwen Liu
Superconductivity
Sida Tian, Naoto Tsuji and Dirk Manske
We extend the well-established action of the
Higgs mode in $s$-wave
superconductors to include
quantum fluctuations (QFs). We find that already one-loop
quantum corrections to the
Higgs propagator shift its eigenfrequency below the superconducting energy gap $2\Delta$. Consequently, the
Higgs mode appears as an undamped pole below the quasiparticle continuum, leading to drastically sharper experimental signatures. We demonstrate this by calculating two characteristic fingerprints of the
Higgs mode, namely in Third Harmonic Generation (THG) and inelastic Raman scattering signals. More generally, gaps measured in $s$-wave
superconductors with different experimental techniques (such as scanning tunneling microscope and Raman scattering) may be different due to fluctuation corrections. Since already arbitrarily weak QFs lead to the shift and to the new pole, our results shed some light on other amplitude modes even for systems with weak QFs, including charge density waves, (anti-) ferromagnets, or cold atom fermionic condensates.
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Soft Condensed Matter
Passivity-Driven Order-Disorder Transitions in Self-Aligning Active Matter
Weizhen Tang, Amir Shee, Zhangang Han et al. (+3 more)
We study dense mixtures of passive and active self-aligning disks with isotropic or anisotropic mobility. We find that the passive fraction controls an order-disorder transition that is continuous in the isotropic case and discontinuous in the anisotropic one. A mean-field equation derived from the microscopic heading dynamics captures this dichotomy. Near the transition, both ordered regimes can exhibit multiple metastable oscillating or rotating states, depending on the spatial arrangement of passive particles and
lattice defects, but with different transient dynamics: Systems with isotropic mobility visit multiple long-lived attractors during each simulation while systems with anisotropic mobility are trapped by a single attractor. Our results reveal the passive fraction as a physically relevant control parameter in active systems, leading to rich self-organizing dynamics.
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All authors Weizhen Tang, Amir Shee, Zhangang Han, Pawel Romanczuk, Yating Zheng, Cristián Huepe
Quantum Gases
Kardar-Parisi-Zhang physics in optically-confined continuous polariton condensates
Mikhail Misko, Natalia Starkova and Pavlos G. Lagoudakis
Kardar-Parisi-Zhang (KPZ) scaling has been observed in discrete polariton
lattices, enabled by engineered band structures that stabilize the condensate. Whether this universality extends to intrinsically continuous systems with natural noise regularization remains an open question. We propose and numerically demonstrate KPZ scaling in a continuous quasi-one-dimensional polariton condensate stabilized by optical confinement in the transversal direction. Large-scale simulations of the
stochastic Gross-Pitaevskii equation, with experimentally relevant parameters, reveal temporal and spatial scaling exponents of the two-point phase correlation function betaC = 0.30(5) and alfaC =0.46(8), and Tracy-Widom one-point phase fluctuation statistics, yielding robust KPZ dynamics intrinsic to the continuous polariton fluid.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Quantum instanton theory for metastable collective spin systems
Krzysztof Ptaszynski, Maciej Chudak and Massimiliano Esposito
Collective
spin systems – driven-dissipative
spin ensembles whose
unitary and dissipative processes act uniformly on all
spins, allowing their dynamics to be described as a single macrospin – play an important role in atomic and solid-state physics. Their intrinsic nonlinearity gives rise to multiple long-lived metastable states that ultimately relax to a unique most probable state. This dominant state can change with a control parameter, leading to first-order phase transitions. We develop a real-time instanton approach based on
quantum quasiprobability dynamics that captures the stationary state in the large-
spin limit and the asymptotic scaling of relaxation rates. We further show that these features are not accurately described by the previously applied semiclassical Wigner approach due to its neglect of non-Gaussian fluctuations.
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Other Condensed Matter
Static heterogeneity generates apparent universality in first-passage bursty dynamics
Morten Møller, Philipp Rahe, Sadegh Ghaderzadeh et al. (+2 more)
Processes involving bursts of activity separated by quiescent periods occur across diverse systems and scales. In human dynamics, these phenomena have been described by power-law inter-event time distributions, $P(t)\sim t^{-\alpha}$, with putative universality classes $\alpha=1$ and $\alpha=\frac{3}{2}$ having been proposed. Whether the observed $\alpha = 1$ scaling reflects intrinsic scale-free dynamics or instead emerges from heterogeneous underlying rates has been debated at length. We address this question in a canonical physical system for first-passage dynamics: two-dimensional molecular
diffusion detected by the tip of a scanning tunnelling microscope. The resulting inter-pulse time distributions exhibit the same apparent truncated power-law form reported for human activities such as email communication, web browsing, and library loans. Maximum-likelihood estimation and model comparison decisively favor a Kohlrausch-Williams-Watts–tempered power law, $P(t)\propto t^{-\alpha}\exp\left(-(t/t_c)^\beta\right)$, with $\alpha \sim 1$. Kinetic Monte Carlo simulations reproduce this behavior, showing that the apparent $\alpha \sim 1$ scaling is confined to a finite time window and arises from tip-induced spatial heterogeneity, not scale invariance.
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All authors Morten Møller, Philipp Rahe, Sadegh Ghaderzadeh, Elena Besley, Philip Moriarty
Materials Science
Disentangling the ferroelectric phases of epitaxial hafnia
Johanna van Gent Gonzalez, Ewout van der Veer, Yulei Li et al. (+2 more)
Since its discovery, ferroelectric hafnia has been extensively studied due to its CMOS-compatibility and ability to remain polarized at sub-10 nm thicknesses. The ferroelectric behaviour is generally attributed to a polar orthorhombic (OIII) phase. However, a second polar phase with rhombohedral
symmetry (R-phase) has also been reported in epitaxial films. The nature of the R-phase remains disputed due to the subtle differences with the OIII-phase when probed by standard thin film characterisation techniques. Given the functional properties of ferroelectrics are crucially determined by the
crystal symmetry, resolving this matter is imperative. In this work, we settle the controversy through extensive 3D reciprocal space surveys made possible via synchrotron-based grazing incidence diffraction from epitaxial films of both phases. These experiments, together with direct comparison of their temperature dependence and electrical responses, conclusively establish them as two distinct phases and provide insight into their key characteristics.
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All authors Johanna van Gent Gonzalez, Ewout van der Veer, Yulei Li, Daniel A. Chaney, Beatriz Noheda
Materials Science · Cross-listed from physics.optics
Optical Modulation Due to Energy Exchange Between Photonic and Exciton Modes in the Intermediate Coupling Regime
Evripidis Michail, Sander A. Mann, Kamyar Rashidi et al. (+4 more)
Actively tunable photonic devices are vital for next-generation optoelectronics requiring rapid switching and high bandwidth. Although organic optoelectronic devices have found wide application, their use as optical modulators has been limited by low absorption in the critical near-infrared (NIR) region, slow response time, and weak nonlinearities. To address these limitations, we developed a scheme based on intermediate
exciton-
photon coupling in a NIR absorbing squaraine-dye based photonic structure. Using energy-momentum resolved pump-probe spectroscopy, we show that the sign and magnitude of the optical response of our system depends strongly on the energy detuning between the excitonic and photonic modes. These data are analyzed using temporal coupled-mode theory to show that near resonance, a distinct energy exchange process emerges in the cross-over regime between strong and weak light-matter coupling. This effect enables dynamical control over the photoinduced response, providing a pathway for broadband optical signal modulation extending into the NIR spectral region.
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All authors Evripidis Michail, Sander A. Mann, Kamyar Rashidi, Christoph Lambert, Vinod M. Menon, Andrea Alu, Matthew Y. Sfeir
Mesoscale and Nanoscale Physics
Kinetic simulation of magnetic-field-tuned hydrodynamic electron transport in graphene corbino disk
Chuang Zhang, Meng Lian, Hong Liang et al. (+3 more)
Hydrodynamic electron transport, in which electrical transport in solids resembles fluid hydrodynamics when momentum-conserving electron-electron scattering dominates, has attracted much
attention over the past decade. However, its thermal aspects have received considerably less
attention. In this paper, electron transport in a
graphene Corbino disk is systematically simulated by solving the stationary Boltzmann transport equation with a dual-relaxation-time Callaway model, where momentum-conserving and momentum-relaxing scatterings are explicitly distinguished. By varying the
magnetic field intensity and the scattering rates, the electric charge and heat flux responses are compared across the diffusive-to-hydrodynamic crossover under electric-field or temperature-gradient drives. It is shown that
magnetic-field-induced deflection of both fluxes is strongly enhanced in the hydrodynamic regime but nearly suppressed in the diffusive regime. Under electric-field driving, a pronounced temperature rise is observed in the hydrodynamic regime due to reduced dissipation, while the diffusive regime remains nearly isothermal. Under temperature-gradient driving, the deflection is reversed relative to the electric-field case. These findings establish that thermal behaviors could provide a sensitive and independent diagnostic of electron hydrodynamics, with the
magnetic field being identified as an effective discriminator between collective and dissipative conduction.
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All authors Chuang Zhang, Meng Lian, Hong Liang, Xiaokang Li, Zhaoli Guo, JingTao Lü
Strongly Correlated Electrons
High-temperature charge-4e superconductivity in SU(4) interacting fermions
Shao-Hang Shi, Zhengzhi Wu, Jiangping Hu et al. (+1 more)
The condensation of electron quartets, known as charge-4e superconductivity (SC), represents a novel
quantum state of matter beyond the standard paradigm of Cooper pairing. However, concrete microscopic models realizing this phase in two dimensions remain a central challenge. Here, we introduce a non-engineered and sign-problem-free model, unambiguously demonstrating the emergence of a robust and high-temperature charge-4e SC phase using unbiased
quantum Monte Carlo simulations. At zero temperature, the phase diagram reveals that charge-4e SC is the primary ground state in the strong-coupling regime. At finite temperature in the absence of charge-2e SC, we identify charge-4e SC through a Berezinskii-Kosterlitz-Thouless transition, marked by a universal jump in the superfluid stiffness consistent with a condensate of charge 4e. Remarkably, the transition temperature Tc increases nearly linearly with interaction strength, providing a robust mechanism for high-Tc quartet superconductivity. Furthermore, spectral analysis reveals a prominent pseudogap above Tc arising from strong phase fluctuations. Our results establish a canonical and numerically exact model system for charge-4e superconductivity, offering crucial guidance for its realization in experimental platforms such as moiré materials and ultracold atomic systems.
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All authors Shao-Hang Shi, Zhengzhi Wu, Jiangping Hu, Zi-Xiang Li
Superconductivity
Type II Lifshitz invariant and optically active Higgs mode in time-reversal symmetry broken superconductors
Raigo Nagashima, Chihiro Mamiya and Naoto Tsuji
Lifshitz invariant is a
symmetry-allowed term in the Ginzburg-Landau free energy of an ordered phase, involving the order parameters and a single spatial derivative, which serves as a source of unusual optical responses. Here we introduce a “type II" Lifshitz invariant for
superconductors, which changes its sign under the particle-hole transformation and can be distinguished from the ordinary particle-hole even “type I" Lifshitz invariant. We show that the type II Lifshitz invariant appears only in
superconductors that break time-reversal
symmetry and allows the
Higgs mode to be visible in the optical conductivity spectrum. We provide a classification of all pairs of irreducible corepresentations of order parameters in the
magnetic point groups that admit a type II Lifshitz invariant. We also numerically calculate the optical conductivity for various models of time-reversal
symmetry broken multiband
superconductors, finding agreement with the group-theoretical analysis. Our results establish a universal class of time-reversal
symmetry broken
superconductors hosting an optically active
Higgs mode.
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Mesoscale and Nanoscale Physics
Poor man's Majorana bound states in quantum dot based Kitaev chain coupled to a photonic cavity
Francesco Buonemani, Alvaro Gómez-León, Marco Schirò et al. (+1 more)
Quantum dot based platforms offer a promising route towards realizing the Kitaev chain
Hamiltonian hosting Majorana bound states (MBSs). Poor man's MBSs arise in a two-site Kitaev chain when the parameters of the system are fine-tuned to the sweet spot. Based on our previous work [Phys. Rev. B 111, 155410 (2025)], we consider a microscopic model for the Kitaev chain based on
quantum dots with proximity effect embedded in a photonic cavity. We find that the
photon coupling in the microscopic model yields an effective
Hamiltonian where the cavity affects the pairing term. However, we demonstrate that even in this case, it is possible to screen particle interactions and reach the sweet spot condition for the emergence of the poor man's MBSs. In particular, we find that attractive particle interactions can be canceled for the cavity prepared in the zero-
photon state, while repulsive ones can be screened with a cavity prepared in the one-
photon state. Furthermore, in case of a large number of
photons in the cavity, we find that the hopping amplitudes are suppressed resulting in a degenerate spectrum. This motivates the use of
quantum light for engineering poor man's MBSs with cavity
embedding.
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All authors Francesco Buonemani, Alvaro Gómez-León, Marco Schirò, Olesia Dmytruk
Soft Condensed Matter
Multispecific DNA-Coatings for Self-Assembly
T.C.M. Stevens, A. van der Sluis, I.K. Voets et al. (+1 more)
DNA-coated particles are promising as building blocks for functional and finite-sized assemblies because they can be programmed with orthogonal interactions owing to the sequence-specific hybridization of DNA strands. To fully exploit this programmability, it is important to develop particles with coatings that incorporate multiple distinct DNA sequences in tunable ratios and to understand how the coating composition influences self-assembly. Here, we compared two strategies to graft multiple DNA sequences in tunable and well-defined ratios on micron-sized colloidal particles. We found that a method based on click chemistry yielded mixed coatings with large batch-to-batch variation in the composition, while a method based on isothermal DNA polymerization produced coatings of predictable composition with a precision of a few percent, but requires reaction rate measurements for each new sequence in the coating. Our self-assembly experiments showed that, even with precise control over coating composition,
equilibrium co-assembly of multiple types of DNA-coated particles is limited by the number of interactions that are reversible within the same narrow temperature window. This finding highlights the need to explicitly incorporate sequential assembly pathways into structure design, with coating composition dictating the order of binding events, Together, our results show how systematic tuning of interaction strength and sequential assembly through multispecific DNA coatings is a prerequisite for the experimental realization of finite-sized and dynamic structures that have so far remained largely theoretical.
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All authors T.C.M. Stevens, A. van der Sluis, I.K. Voets, P.G. Moerman
Materials Science
Controllable highly oriented skyrmion track array in Fe3GaTe2
Yunhao Wang, Shiyu Zhu, Chensong Hua et al. (+15 more)
Magnetic skyrmions are emerging as promising candidates for next-generation information technologies, while the realization of scalable skyrmion
lattices with tailored configurations is essential for advancing fundamental skyrmion physics and developing future applications. Here we achieved the controllable generation and regulation of a large-area, highly oriented skyrmion track array (STA) in
ferromagnetic Fe3GaTe2 using a vector
magnetic field manipulation technique. The orientation and ordering of STA, along with the types and density of skyrmions, are precisely controlled by modulating parameters during the manipulation. The critical roles of in-plane
magnetic fields and Dzyaloshinskii-Moriya interaction in STA generation is further confirmed by micromagnetic simulation. Our findings develop a strategy for engineering large-area and highly-oriented skyrmion configurations, offering a new pathway for the future application of next-generation spintronic and information technologies.
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All authors Yunhao Wang, Shiyu Zhu, Chensong Hua, Guojing Hu, Linxuan Li, Senhao Lv, Jianfeng Guo, Jiawei Hu, Runnong Zhou, Zizhao Gong, Chengmin Shen, Zhihai Cheng, Jinan Shi, Wu Zhou, Haitao Yang, Weichao Yu, Jiang Xiao, Hong-Jun Gao
Statistical Mechanics
Thermodynamic Geometry of Relaxation
Hao Wang, Li Zhao, Shuai Deng et al. (+1 more)
While the geometry of
equilibrium states and driven non-
equilibrium processes is clearly understood, a
geometric description for relaxation towards
equilibrium is still lacking. Here, we propose a thermo-
geometric measure based on the Rayleigh quotient, reformulating relaxation as a fundamental competition between entropic stiffness and frictional dissipation. Taking a van der Waals gas with two dissipation channels as an example, we explicitly demonstrate its relaxation landscape. Particularly, we find that upon approaching the critical temperature $T_c$, the slow-mode relaxation rate vanishes linearly as $\lambda_s \propto (T-T_c)/T_c$, indicating critical slowing down. This study completes the thermodynamic geometry framework, providing a general tool for characterizing the relaxation dynamics of complex systems.
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All authors Hao Wang, Li Zhao, Shuai Deng, Yu-Han Ma
Materials Science · Cross-listed from physics.optics
Toroidal Plasmonic Nanodimers for Enhanced Near-Infrared Emission in Heterostructured InP Quantum Dots
Arda Gulucu and Emre Ozan Polat
Near-infrared (NIR) emitters operating in the 650-900 nm range are highly attractive for imaging and sensing in turbid media; however, cadmium-free InP-based
quantum dots (QDs) often suffer from limited brightness due to nonradiative pathways and inefficient
photon outcoupling. In particular, heterostructured InP QDs can exhibit band
alignments that induce partial spatial separation of charge carriers, leading to reduced electron-hole wavefunction overlap. This modifies intrinsic recombination dynamics and enhances the sensitivity of their emission to the surrounding photonic environment. Here, we investigate silver toroidal plasmonic nanoantenna dimers (Ag TPNDs) through finite-difference-time-domain (FDTD) simulations as a geometry-tunable platform for enhancing NIR emission of heterostructured InP-based QDs. The coupled toroidal geometry supports strongly confined bonding modes that generate intense nanogap hotspots, while its resonance can be systematically tuned through the toroid aspect ratio. By spectrally aligning the
antenna response with QD emission bands (675-845 nm), we achieve large Purcell enhancements together with high
quantum efficiencies, demonstrating efficient conversion of enhanced decay rates into radiative emission. We further show that nanometer-scale variations in emitter-
antenna separation strongly modulate the radiative rates and spectral response. These results establish toroidal plasmonic nanodimers as a
topology-driven platform for controlling emission in NIR
quantum emitters and for advancing NIR nanophotonic applications.
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Materials Science · Cross-listed from physics.app-ph
Spontaneous Emission, Work Potential and Relaxation-Limited Processes in Setting Limits on Solar Energy Conversion Efficiency
Sumanta Mukherjee
Understanding the thermodynamics of radiation and the
quantum-mechanical interactions between light and matter is important both for theoretical purposes and for technological advances, such as determining the limits of key processes like light-to-usable-energy conversion efficiencies. In this report, we discuss the physics of these two aspects, considering spontaneous emission as a pathway, and highlight the limitations of such descriptions in assessing energy-harvesting efficiency. In view of these limitations, we adopt a simplified approach to evaluate the exergy and work potential of radiation, providing a framework for assessing various aspects of light-to-usable-energy conversion efficiency. Our approach allows a theoretical estimate of the thermodynamic maximum limit for light-to-usable-energy conversion, which is approximately 76%. We validate these exergy and work potential estimates by modeling and accurately reproducing the Shockley-Queisser limit (~ 33.3%), which imposes a practical constraint on
solar-to-usable-energy conversion efficiency. Beyond exergy considerations, our model incorporates processes such as spontaneous emission, nonradiative thermal losses, and
photon upconversion, allowing us to evaluate their roles. The model further suggests that, under certain conditions, the maximum conversion efficiency can reach approximately 48%, for example with multijunction
solar cells or via
photon upconversion. These findings further suggest that the true thermodynamic limit for light-to-usable-energy conversion may be much higher (approximately 76%). However, accurately estimating this limit requires a more complete understanding of the thermodynamics of light, light-matter interactions, and the connection between them.
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Materials Science
Towards Non-van der Waals 2D Topological Insulators
Mani Lokamani, Gustav Bihlmayer, Gregor Michalicek et al. (+3 more)
Non-van der Waals two-dimensional (2D) materials derived from strongly bonded non-layered
crystals have recently emerged as a novel and rising platform for nanoscale research. While uncovering and tuning their (opto-)electronic, catalytic, and
magnetic properties has been the focus of intense research, the impact of
spin-orbit coupling (SOC) onto their electronic structure has not yet been explored in detail. Studying these effects is, however, particularly relevant due to their surface cation termination and the presence of heavy elements in several representative compounds. Here, we investigate the effect of SOC onto the electronic structure of 2D AgBiO3, NaBiO3, and SbTlO3. While the first two systems show negligible band renormalization upon inclusion of relativistic effects around the band gap, SbTlO3 showcases a large SOC induced splitting (229meV) for the lowest conduction bands associated with a band inversion. Substitution of Tl with Pb forming SbPbO3 brings the band-inverted feature to the
Fermi level. Analysis of topological invariants and investigation of edge states of zig-zag and armchair ribbons within the 200meV gap confirms the topological nature of the band splitting. Our work thus establishes a foundation for the systematic study of robust non-van der Waals 2D topological
insulators.
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All authors Mani Lokamani, Gustav Bihlmayer, Gregor Michalicek, Daniel Wortmann, Stefan Blügel, Rico Friedrich
Statistical Mechanics
Coarse Graining Reveals a Fluctuation-theorem-like Asymmetry in Financial Markets
Jian Gao, Lufeng Zhang, Ping Fang et al. (+4 more)
Fluctuation
theorems show how coarse graining transforms microscopic
symmetry into observable irreversibility. Here we ask whether an analogous symmetrybased diagnostic can be constructed for financial
markets. At the microscopic level, each transaction pairs a buyer and a seller, whereas trading decisions are typically made from coarse-grained price histories. Using symmetric takeprofit and stop-loss rules, we compare the holding-time distributions of long and short trading ensembles generated from the same price series. Across equityindices, individual stocks and cryptocurrencies, the log-ratio of the two distributions shows a robust crossover. It remains nearly constant at short durations but becomes linear in the tail, implying an exponential directional asymmetry. The tail slope defines an effective
market temperature, an operational measure of fluctuation intensity on the chosen observation scale. A Bachelier first-passage
benchmark captures the exponential tails but not the asymmetry, because long and short positions share the same leading decay rate. By contrast, short-time correlations between overlapping positions provide a minimal mechanism for the asymmetry by generating direction-dependent subleading relaxation spectra in a coarse-grained Markov description. Together, these results establish a fluctuation-
theorem-like diagnostic of irreversibility in financial
markets and, more broadly, in complex systems accessible only through coarse-grained observables.
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All authors Jian Gao, Lufeng Zhang, Ping Fang, Pu Ke, Jin Wu, Yue Liu, Haijun Zhou
Superconductivity
Fermi-liquid versus non-Fermi-liquid/'strange-metal' fits to the electrical resistivity in the quantum critical magnetic regime of an unconventional superconductor
W. Knafo, T. Thebault, K. Somesh et al. (+4 more)
The question of a possible
quantum critical point lying inside of a superconducting phase is central for understanding unconventional superconductivity. In various unconventional
superconductors, non-
Fermi-
liquid/'strange-metal' $T^{n}$ variations, with $n<2$, of the electrical resistivity have been identified as the signature of
magnetic quantum criticality. However, a difficulty is to prove experimentally that a non-
Fermi-
liquid/'strange-metal' law identified at temperatures above the superconducting temperature is the signature of an intrinsic zero-temperature
quantum critical regime. In the heavy-
fermion paramagnet UTe$_2$, unconventional superconductivity develops in the vicinity of a metamagnetic
quantum phase transition induced by a
magnetic field, and the
quantum critical
magnetic properties are suspected to play a role for the superconducting mechanism. In this work, we present a comparative analysis of electrical resistivity data collected on two UTe$_2$ samples of different qualities, in
magnetic fields tilted by angles $\theta\simeq35-40$~$^\circ$ from $\mathbf{b}$ to $\mathbf{c}$. Fits to the data have been performed either with a
Fermi-
liquid function $\rho=\rho_0+AT^{2}$ or with a non-
Fermi-
liquid/'strange-metal' function $\rho=\rho_0+A_nT^n$. Near to a superconducting phase induced beyond 40~T, non-physical residual resistivities $\rho_0<0$ are extracted from the $T^n$ fits, revealing that a 'hidden'
Fermi-
liquid $T^2$ regime may be ultimately recovered at low temperature. The results obtained here highlight the importance to investigate high-quality samples with low residual resistivity to confirm - or not - the presence of a suspected 'hidden'
quantum critical behavior masked by superconductivity.
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All authors W. Knafo, T. Thebault, K. Somesh, G. Lapertot, G. Knebel, D. Braithwaite, D. Aoki
Materials Science
Magneto-optical imaging of macroscopic altermagnetic domains in MnTe
Gakuto Watanabe, Soichiro Yamane, Ryotaro Maki et al. (+6 more)
Altermagnets are a new class of magnets accompanying global time-reversal
symmetry breaking (TRSB) without net magnetization. The TRSB results in formation of novel altermagnetic domains. Features of altermagnetic domains, in particular their responses to external stimuli, are essentially important but yet unexplored. Here, we report visualization of bulk altermagnetic domains in MnTe based on scanning magneto-optical Kerr-effect microscopy using telecom infrared wavelength. We found two distinct TRSB domains with large Kerr rotations that do not scale with its tiny bulk magnetization. We also revealed controllability and stability of domains against
magnetic or thermal perturbations. Our first observation of altermagnetic domains using a laboratory-scale simple optical technique showing their movable nature provide firm bases for future fundamental and application studies of altermagnets.
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All authors Gakuto Watanabe, Soichiro Yamane, Ryotaro Maki, Atsutoshi Ikeda, Akimitsu Kirikoshi, Junya Otsuki, Takuya Aoyama, Kenya Ohgushi, Shingo Yonezawa
Soft Condensed Matter
Effect of sub-critical fluid shear flow on granular bed strength
Dong Wang, Sophie Bodek, Nicholas T. Ouellette et al. (+2 more)
Interactions between fluids and granular materials are prevalent on the Earth's surface. In the case of fluid flow over a sediment bed, the fluid imparts a shear stress to the granular materials. When the applied shear stress is above a critical value, the grains become entrained in the fluid flow. Prior experimental studies have shown that granular beds subjected to a sub-critical fluid flow can strengthen in the same direction as the sub-critical flow. In contrast, granular beds can become weaker in the direction opposite to the sub-critical fluid flow. To investigate the grain-scale mechanisms that control directional strengthening and weakening, we perform discrete element method (DEM) simulations of granular beds subjected to model fluid flows in two (2D) and three (3D) dimensions with varied inter-particle static friction coefficients and conditioning flow speeds. In these studies, the sub-critical grain motion does not cause significant bed compaction. Instead, we find that the strength of a granular bed in a particular direction is highly correlated with the fraction of surface grains that can be dislodged by a fluid force applied in that direction. Further, the anisotropic bed strength only persists over a finite time scale that is set by the Shields number. We also show that inter-particle static friction is not required for bed strength anisotropy, but varying the friction affects the magnitude of the anisotropy. This research enhances the grain-scale understanding of erosion of granular beds caused by fluid flows and underscores the importance of tracking the history of the fabric of the bed surface since it couples strongly to bed strength.
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All authors Dong Wang, Sophie Bodek, Nicholas T. Ouellette, Mark D. Shattuck, Corey S. O'Hern
Soft Condensed Matter · Cross-listed from physics.comp-ph
Spectrally Accurate Simulation of Axisymmetric Vesicle Dynamics
M.A. Shishkin
We present a meshless numerical method for simulating the dynamics of axisymmetric vesicles in a viscous medium. Key innovations include: (1) adaptive reparameterization based on local length scales, reducing the number of required harmonics; (2) gauge dynamics for maintaining optimal parameterization; (3) error control near the
symmetry axis; and (4) spectrally accurate quadrature schemes for singular integrals. The method achieves high accuracy and computational efficiency for simulating lipid
bilayer dynamics and related problems in soft matter physics.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Light-propelled microparticles based on symmetry-broken refractive index profiles
Julian Jeggle, Matthias Rüschenbaum, Adrian Paskert et al. (+7 more)
Active colloidal microparticles require reliable actuation to sustain directed motion. Light-based propulsion is particularly attractive as it provides persistent energy supply and enables direct spatiotemporal control. Here, we introduce 3D-printable particles with
symmetry-broken refractive index profiles (SBRIP particles) that achieve propulsion through direct momentum transfer from asymmetric light refraction. Internal refractive-index gradients provide optical
symmetry breaking independent of external shape, fundamentally decoupling propulsion from particle geometry. Geometrically
symmetry-broken particles with a homogeneous refractive index are another special case, where propulsion originates from refractive contrast at the boundary instead of within the particle. Unlike conventional systems relying on absorption or reflection, this transparency-based mechanism minimizes heating and mitigates shadowing in bulk suspensions. We present a theoretical framework for refractive propulsion as well as numerical simulations of the SBRIP particles using raytracing and the finite volume method. This is complemented by experiments, validating the momentum transfer mechanism using particles with
geometric symmetry breaking. The high transparency of our particles ensures deep light penetration, enabling the realization of volumetric active matter. This opens pathways toward adaptive nonlinear optical materials where light-driven particle reorganization modulates the local refractive index, establishing a dynamic feedback loop between the optical field and the material structure.
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All authors Julian Jeggle, Matthias Rüschenbaum, Adrian Paskert, Ivan Kalthoff, Elena Vinnemeier, Jesco Schönfelder, Jörg Imbrock, Cornelia Denz, Marcel Rey, Raphael Wittkowski
Materials Science
Reversable phase transitions in ferroic two-dimensional Nb2O2I4 through optically excited coherent phonons
Chuanlin Liu, Dan Liu, Jie Guan et al. (+1 more)
We investigate optically induced phase transitions in the two-dimensional (2D) ferroelectric (FE) material Nb2O2I4 using real-time time-dependent density functional theory (rt-TDDFT). Our results demonstrate that tailored
laser pulses can activate specific coherent
phonon modes. Specifically, the anharmonic atomic distortions of the A1-1 and A1-2 modes at the {\Gamma}-point facilitate the reversal of in-plane polarization. By fine-tuning
laser parameters, additional
phonon modes at both the Y and {\Gamma} points are excited. The resulting nonequilibrium atomic dynamics enable the formation of previously unreported ferroic phases, including three antiferroelectric (AFE) phases and one ferrielectric (FiE) phase. Notably, these optically induced phases can be reverted to the initial FE state using appropriate techniques. This controllable reversibility among multiple ferroic phases positions 2D Nb2O2I4 as a highly promising candidate for next-generation electronic storage applications.
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All authors Chuanlin Liu, Dan Liu, Jie Guan, Chao Lian
Soft Condensed Matter
Highly coarse-grained polarisable water models for mesoscopic simulations
Michael A. Seaton, Benjamin T. Speake and Ilian T. Todorov
Modelling micro- and meso-scopic scale thermodynamic and transport properties of soft condensed matter hinges upon its representation. This is especially relevant for polar solvents such as water, since these require effective representation of their dielectric nature as driven by molecular charge distributions and molecular network structuring. The dielectric nature of a medium leads to complex phenomena such as local polarisability response and restructuring near interfaces in reaction to changes in local charge distributions. Inclusion of such phenomena when using larger-than-atomistic techniques such as coarse-grained molecular dynamics (CG-MD) and dissipative particle dynamics (DPD) is still an open question, to which we provide a novel way to consider and justify the necessary and suitable coarse-graining level, enabling us to compare new polar CG models' performance against that of an underlying atomistic model. We polarise our previous non-polar nDPD water model to prepare it for use in simulations of
liquid electrolytes as well as solvated organic membranes and measure its fitness to serve as a dielectric medium by comparing its properties to those of the TIP3P water model, while simultaneously observing changes to properties already represented well by the non-polar model.
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Strongly Correlated Electrons
Unconventional plasmon dynamics due to strong correlations in Sr$_2$RuO$_4$
Juraj Krsnik, Dino Novko, Fabian B. Kugler et al. (+2 more)
Plasmon modes, their dispersion, and the onset of damping when approaching the electron-hole continuum are well understood when electron correlations are weak. However, we know little about how this picture is modified and what additional features emerge in strongly correlated materials. Here, we present a fully ab initio approach to plasmon excitations that combines density functional theory with dynamical mean-field theory, and we use it to reconcile controversial electron energy-loss spectroscopy results in Sr$_2$RuO$_4$. In particular, we show that electronic correlations reproduce the plasmon dispersion, while generating a large intrinsic width already below the electron-hole continuum. An additional high-energy peak reflecting transitions between incoherent features and a sharp increase of the plasmon's energy-momentum dispersion, akin to waterfalls in photoemission spectroscopy, are identified as genuine correlation effects.
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All authors Juraj Krsnik, Dino Novko, Fabian B. Kugler, Osor S. Barišić, Karsten Held
Statistical Mechanics
Emergence of Open Chemical Reaction Network Thermodynamics within Closed Systems
Benedikt Remlein, Massimiliano Esposito and Francesco Avanzini
Under which conditions do the dynamics and thermodynamics of open chemical reaction networks (CRNs), grounded on the notion of idealized chemostats that exchange selected species, emerge from underlying closed CRNs? While open CRNs provide the standard framework to describe out-of-
equilibrium chemical systems, real systems are finite and ultimately relax to
equilibrium, leaving the status of this description conceptually unresolved. Here, we address this fundamental question. We show that open-CRN behavior arises as an asymptotic regime of closed CRNs when two physically minimal and transparent conditions are met: a time-scale separation, whereby fast reactions effectively act as exchange mechanisms, and an abundance separation, whereby a subset of species behaves as chemostats with diverging chemical capacity. In this regime, both the
stochastic dynamics and the thermodynamic structure - including local detailed balance,
entropy production, and free-energy balance - emerge to leading order from the underlying closed CRN. We further predict that this regime persists up to a characteristic time proportional to the scale of the abundance separation, thereby providing an experimentally accessible criterion for estimating how long a finite closed system behaves as an open CRN. Our results apply to arbitrary stoichiometries. They show that chemostats need not be introduced as external idealizations, but instead arise as emergent thermodynamic structures within closed systems, providing a unified and physically grounded foundation for the nonequilibrium thermodynamics of CRNs.
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Materials Science
Propagation of laser-generated GHz surface acoustic wavepackets in FeRh/MgO(001) below and above the antiferromagnetic-ferromagnetic phase transition
Ia. A. Mogunov, A. Yu. Klokov, N. Yu. Frolov et al. (+6 more)
Magnetoacoustic devices that harness the strong coupling between acoustic waves and
magnons have emerged as a promising platform for energy-efficient spintronics.
Laser-generated pulsed surface acoustic waves (SAWs) are particularly attractive for such applications, offering broadband frequency content up to the gigahertz (GHz) range, remote excitation without lithographic patterning, and surface localization for efficient on-chip integration. In this work, we present a comprehensive experimental study of
laser-generated SAW pulses in the Fe49Rh51/MgO(001) system. A thin film of the near-equiatomic FeRh
alloy serves both as an opto-acoustic transducer and as a mechanical load that modulates SAW propagation. The
antiferromagnetic to
ferromagnetic phase transition in FeRh, occurring slightly above room temperature, is accompanied by abrupt changes in its elastic properties, enabling controlled modification of the SAW excitation efficiency and dispersion characteristics by tuning the sample temperature and
laser fluence. Using 160 fs
laser pulses for excitation and time-resolved Sagnac interferometry for detection, we evaluated key SAW parameters, including amplitude, spectral content, phase and group velocities, and their in-plane anisotropy. Particular emphasis is placed on the dispersion relation and its anisotropy, which govern the coherent interaction between
phonons and
magnons and are determined primarily by the FeRh film.
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All authors Ia. A. Mogunov, A. Yu. Klokov, N. Yu. Frolov, A. I. Sharkov, A. V. Protasov, G. E. Zhezlyaev, D. I. Devyaterikov, V. I. Zverev, A. M. Kalashnikova